The availability of genetic and physical maps of prokaryotic genomes is important in revealing basis principles of genome organization and evolution, in addition to providing models for the analysis of more complex genomes. For some bacteria, such as Neisseria gonorrhoeae, no genetic map is available, and the range of genetic tools is limited. The gonococcus is unusual in possessing a substantial number of reiterated genes and sequence elements, and in demonstrating extensive rearrangement and recombination of its chromosome. Despite the presence of several known families of repeated genes, the genome of the gonococcus is relatively small (2300) kb). Therefore, the gonococcus provides a model system in which to gain insight into the organization, evolution, and function of repeated genes and sequence elements, in a way that has not been possible with other prokaryotic systems. The specific aim of this project is the construction of a physical map of the gonococcal chromosome, and the location of identified single-copy and multi-copy genes on the map. The location and arrangement of repeated sequence elements will also be determined. A macro-restriction map of the chromosome will be constructed, using pulsed-field electrophoresis to resolve large DNA fragments generated by digestion with enzymes having rare recognition sequences. Appropriate restriction enzymes have already been identified. The resolution of the map will be increased by further restriction mapping of selected regions, or by cosmid cloning of overlapping fragments. The location of genes and repeated sequence elements will be determined by Southern blotting experiments, using appropriate probes derived from cloned gonococcal genes. Some genetic markers will be localized by genetic transformation, using specific DNA fragments as donor DNA. If the mapping experiments reveal the existence of repeated sequences or genes other than those already described, those new genes and elements will be characterized by DNA sequencing, and localized on the map. Maps will initially be constructed for two well-characterized gonococcal strains. If the maps differ, higher-resolution analysis of the regions of difference will be done, to determine what types of chromosomal rearrangements may have occurred.